Vol. 70.] THROUGH THE ANDES OF PERU AND ROL1VIA. :J 



occupy three separate areas, between which the foothills are 

 continued to the ocean border : namely, a northern district, 

 including- the plains of Trujillo and Piura ; a south-central in the 

 neighbourhood of Pisco; and a southern, comprising the pampas 

 of Mollendo and Tacna. 



(ii) — In Southern Peru and the district described in the present 

 paper, the mountain -system of the Andes consists of two main 

 chains — a western, the ' Cordillera Occidental,' which is the con- 

 tinuation of the main Chilian range, and an eastern, the ' Cordillera 

 Oriental. 1 Between these two lies the elevated plateau known as 

 the ' Altaplanicie,' the site of Lake Titicaca. Northwards the 

 chains unite in latitude 14° S., forming the Vilcanota knot, to 

 divide again into three main branches — recognized by Raimondi 

 as a Western ' Cordillera,' following the general direction of the 

 coast ; a Central, separating the valleys of the Apurimac and 

 Mantaro Rivers from that of the Urubamba or Vilcamayo ; and an 

 Eastern separating the Urubamba from the Madre de Dios. In 

 the neighbourhood of Cerro de Pasco the chains reunite to form a 

 second mountain-knot, dividing northwards once more into three. 

 Here the Western Cordillera at its southern end, where it diverges 

 from the knot, splits into two minor parallel chains, the 

 'Cordillera Negra ' and the 'Cordillera Blanca,' separated by 

 the valley of Huaylas. This valley at first follows the strike 

 of the chains to the north-west, but in latitude 9° S. cuts the 

 ' Cordillera Negra ' almost at right angles, to enter the sea in the 

 Bay of Santa north of Chimbote. 



The main Central Cordillera separates the valley of the Maranon 

 from that of the Huallaga ; while the Eastern separates the 

 latter from the Ucayali. 



(iii) — The third region comprises the vast forested area of the 

 Amazon basin, almost impenetrable save along the navigable rivers 

 and the narrow trails leading to gold or rubber camps. The 

 descent from the ' Sierra ' is rapid, and the whole country soon 

 becomes clothed in dense tropical vegetation. Rare open spaces, 

 or p a jo n ales, devoid of trees, enable one, however, to obtain 

 occasional glimpses of the distant landscape. A great part of this 

 country has been explored by Dr. J. W. Evans, who describes 

 a number of small parallel chains running in a north-westerly 

 direction parallel to the main ' Cordillera.' The first of these, 

 bounding the valley of the River Coroico on the east, he has named 

 the Cusali Range. 



III. Main Topographical Features of the Country IN- 

 CLUDED IX THE FlRST SECTION. (AEICA TO THE BOLIVIA S 



• Yungas.') (See Map, PI. X, fig. 2.) 



Our first main traverse, the results of which are included in the 

 following pages, was made through the extreme north of Chile, 

 formerly Peruvian territory, and a part of Bolivia, following the 

 present line of railway as far as La Paz. whence it was continued 



n2 



